Noise reduction strip for shear cut perforator

ABSTRACT

A shear cut perforator having an axially recessed bedroll equipped with resilient roll blades for engagement with and flexing by an anvil blade is provided with a resilient, compressible pad behind the flexing portion of the roll blade to reduce the noise level of the perforator.

United States Patent 1191 Bradley 1111 3,733,949 1451 May 22,1973

[54] NOISE REDUCTION STRIP FOR SHEAR CUT PERFORATOR [75] Inventor: John J. Bradley, Green Bay, Wis.

[73] Assignee: Paper Converting Machine Company, lnc., Green Bay, Wis.

[22] Filed: June 21, 1971 21 Appl. No.: 155,145

[52] US. Cl ..83/348, 83/663 [51] Int. Cl. ..B23d 25/12 [58] Field of Search ..83/ll7, 341, 342,

[56] References Cited UNITED STATES PATENTS 3,264,921 8/1966 Nystrand ..83/342 10/1964 Rowlands ..83/348 6/1965 Bradley ..83/342 Primary Examiner-Andrew R. Juhasz Assistant Examiner-W. Donald Bray Attorney-Dawson, Tilton, Fallon & Lungmus [57] ABSTRACT A shear cut perforator having an axially recessed bedroll equipped with resilient roll blades for engagement with and flexing by an anvil blade is provided with a resilient, compressible pad behind the flexing portion of the roll blade to reduce the noise level of the perforator.

9 Claims, 4 Drawing Figures NOISE REDUCTION STRIP FOR SHEAR CUT PERFORATOR BACKGROUND AND SUMMARY This invention relates to shear cut perforators of the type disclosed in Kwitek US. Pat. No. 2,870,840 and Nystrand US. Pat. No. 3,264,921.

Both of the foregoing patents disclose a shear cut perforator for cutting or perforating a web of toilet tissue or the like. The perforator includes a bedroll which is provided with axially extending recesses in which resilient, flexible roll blades are rigidly mounted. A further recess is provided behind a portion of the roll blade for relieving this portion for flexing, and an anvil blade extends radially inward of the path of travel of the cutting edges of the roll blades to interfere therewith. As the roll blade engages the anvil blade, it flexes into the further recessed portion of the bedroll. The anvil blade is advantageously provided by a series of blades or knives arranged in spiral fashion relative to the roll blade so as to develop a progressive point contact between the roll blade and the anvil blade. Each portion of the roll blade is therefore engaged with the anvil blade for only a very short period of time.

In shear cut perforators of this type the web may be advanced at a lineal speed of the order of up to about 2,000 feet per minute, and during each perforation of the web the roll blade is engaged and flexed inwardly by the anvil blade. Because the blades make contact, considerable noise may develop during operation of the machine. This is particularly so, for example, with toilet paper, in which the web is being transversely perforated on 4% inches centers-the blades interfering at the rate of the order of about 60 times per second.

In the years since shear cut perforators of the type described in US. Pat. No. 2,870,840 have been available it has generally been found that the recess or spacing behind the roll blade to permit flexing thereof should be between about 0.012 to about 0.060 inch. If the spacing exceeds this range, the roll blades may be unduly stressed, but, more importantly, if a smaller spacing is provided, there is insufficient room to permit the required flexing. This can result in an unusable product, accelerated blade wear, blade breakage and unacceptable noise levels. Accordingly, there have been no prior attempts to reduce the noise levels of these perforators which would have required a reduction of this spacing.

I have made the surprising discovery, however, that the noise level of a shear cut perforator can be reduced considerably without materially affecting performance by positioning a pad of resilient, compressible noisedampening material in the recess behind each roll blade. The pad is sized to occupy most of the depth of the recess while leaving a slight spacing or gap between the pad and the blade, and the planar pad extends generally coextensive with the free portion of the blade. Although the resulting spacing between the pad and the unflexed blade is substantially less than the minimum heretofore deemed essential, the pad can be compressed sufficiently by the roll blade to permit the desired flexing. This compression is of the order of about 10 percent to about 30 percent of the thickness of the pad, and the use of the pad does not appear to reduce the life of the roll blades.

DESCRIPTION OF THE DRAWING FIG. 3 is a diagrammatic illustration of the action of the roll blade and anvil knives in providing progressive point contact therebetween; and

FIG. 4 is an enlarged fragmentary view of a portion of FIG. 1.

DESCRIPTION OF SPECIFIC EMBODIMENT In the illustration given the numeral 10 designates a perforating bedroll of the character described in the above-mentioned US. Pat. Nos. 2,870,840 and 3,264,921. As described in those patents, the bedroll is mounted for rotation in the direction illustrated by the arrow and is provided with a longitudinally or axially extending recess 11. Although only a single recess is illustrated in FIG. 1, it will be understood that several circumferentially spaced recesses can be provided, for example, five or six as is commonly the case in industry today. A resilient, flexible blade 12 is positioned within each recess and is rigidly supported by a rigid bearing surface 13 in the recess which supports the lower or inner edge portion of the blade. The blade is clamped against the rigid bearing surface by means of clamp 14 and bolt 15, and a resilient strip 16 may be interposed between the clamp and the blade. The recess 11 is provided with an additional recess 17 behind the outer portion of the blade 12 which permits the outer or upper edge portion of the blade to flex inwardly during cutting. A longitudinally extending back-up block 18 may be secured within the recess 17 by bolt 19 to support the outermost position of the blade against excessive flexure and to control the flexing gap behind the blade.

A resilient, compressible pad 20 is positioned within the further recess 17 outwardly of the back-up block. The pad is substantially planar and extends substantially coextensively with the roll blade, extending from the shoulder 17a of the recess 17 to adjacent the cutting edge 12a of the blade. The length of the blades are conventionally about 4% inches, corresponding to'the width of an ultimately developed retail-sized roll of toilet paper, and the pads may have a corresponding length. The blade width is of the order of three-fourths inch to seven-eighths inch and the thickness is about one thirty-second inch. The pad may be adhesively secured to the back-up block to retain the pad behind the blade as the bedroll rotates during operation.

An anvil blade 21 is secured within a recess 22 in an anvil blade holder 23 by a set screw 24 and a clamping element 25. The blade holder is secured against a bearing surface 26 of a cross beam or anvil block 27 by bolts 28 and spring washers 29. The blade holder 23 is provided with a through bore 30 for receiving the bolt 28, and the bore 30 is larger than the bolt to permit ver-.

tical adjustment of the holder relative to the anvil block by means of adjusting screw 31.

Referring now to FIG. 2, the anvil block or cross beam is designed to support the anvil blades in different angular positions so that the anvil blades or knives occupy a position illustrated by the diagonal line shown I in FIG. 3. The cross beam provides successive bearing faces 26 which are turned in planes varying slightly, as illustrated in FIG. 2, so as to bring the blades to be supported thereby into a spiral arrangement. A knife holder 23 is secured to each of the faces 26 by means of the tapped bolt holes 32 which receive the bolts 28.

As each blade 12 of the bedroll moves in a counterclockwise direction, the blade engages a corresponding knife 21 carried by the knife-holders 23 in a successive movement through the arc of travel between the first anvil knife holder and the last anvil knife holder. Not only is the row of blades 21 shown in FIG. 4 at an angle relative to the roll blade, but each individual blade 21 is at an angle so that the cutting at any instant is at a single point of contact. For example, excellent results at speeds of the order of 2,000 feet per minute are achieved when the anvil blade angle is of the order of 0.220 inch, i.e., one end of each 4% inch long blade is offset Q22O inch from the other relative to the axis of the bedroll or the cutting edge of the roll blade. The anvil blade therefore extends at an angle of about 2.80 from the roll centerline.

As the roll blade 12 contacts each anvil blade, the roll blade is flexed into the supplemental recess 17 against the pad 20. However, the compressible pad permits the blade to flex relatively freely and does not provide sufficient resistance to flexing to shorten the life of the blade to any substantial degree.

I have had good results with a pad having a thickness slightly less than the depth of the supplemental recess in a direction normal to the roll blade, i.e., the distance between the rear face of the blade and the back-up block 18. In one specific embodiment, the roll blade was about one thirty-second inch thick, the spacing or gap between the blade and the back-up block was about 0.040 inch, and the pad was about 0.035 inch. The anvil blade holers were adjusted to provide an interference with the roll blade of about 0.007 inch, i.e., the vertical dimension of the roll blade deflection would be 0.007 inch. Since the roll blades extend at an angle of about 45 when they contact the anvil blades, the deflection of the cutting edge of the roll blade into the supplemental recess along a line normal to the plane of the blade would be 0.007 X 1.414 or about 0.010 inch. The pad would therefore be compressed about 0.005 inch along the outer portion thereof, or about 14 percent of its thickness.

Generally, the thickness of the pad may be about the same as the thickness of the roll blade, and the thickness of the pad relative to the depth of the supplemental recess and the deflection of the roll blade may be such that the pad is compressed from about percent to about 30 percent of its thickness. The depth of the supplemental recess is generally of the order of about 0.030 to about 0.040 inch, and the pad can be sized correspondingly.

I have had particularly good results in forming the pad from polyurethane plastic available from Dewey and Alrny Chemical Division of W.R. Grace & Co. under the name Polyfibron 2. This material is provided with an adhesive backing which can be used to secure the padto the back-up block.

While in the foregoing specification a detailed description of a specific embodiment of the invention is set forth for the purpose of illustration, it is to be understood that many of the details herein given may be varied considerably by those skilled in the art without departing from the spirit and scope of the invention.

I claim:

1. In a web perforating apparatus having a frame, a cutting bedroll mounted for rotation in the frame, and an anvil blade having a cutting edge mounted on the frame adjacent the bedroll, the bedroll having an axially extending recess in the surface thereof and a rigid bearing surface within the recess, a resilient-roll blade rigidly supported on the bearing surface and having an inclined outwardly extending free portion provided with a cutting edge, the bedroll being provided with a further recess adjacent the outwardly extending free blade portion for relieving said free blade portion for flexing, and a resilient compressible pad within said further recess adjacent the roll blade, the cutting edge of the anvil blade being positioned radially inwardly of the' path of travel of the cutting edge of the roll blade to bring the edges of the blades into engagement during rotation of the bedroll whereby the roll blade is flexed and the pad is compressed.

2. The apparatus of claim 1 in which the pad is substantially coextensive with the free blade portion of the roll blade.

3. The apparatus of claim 1 in which the roll blade and the pad are of approximately the same thickness.

4. The apparatus of claim 1 in which the depth of the further recess in a direction normal to the plane of the roll blade is slightly greater than the thickness of the pad.

5. The apparatus of claim 4 in which the difference between the depth of the further recess and the thickness of the pad is about one-half of the distance through which the cutting edge of the roll blade is flexed into the further recess by the anvil blade.

6. The apparatus of claim 1 in which the pad is compressed by about 10 percent to about 30 percent of its thickness by the flexing of the roll blade.

7. The apparatus of claim 1 in which the said further recess has a depth normal to the plane of the roll blade of about 0.040 inch and the pad has a thickness of about 0.035 inch.

8. The apparatus of claim 7 in which the cutting edge of the roll blade is flexed by the anvil blade a distance of about 0.010 inch from the plane of the roll blade.-

9. The apparatus of claim 1 in which the anvil blade extends at an angle of about 2.8 to the roll blade.

a: t n- 1 

1. In a web perforating apparatus having a frame, a cutting bedroll mounted for rotation in the frame, and an anvil blade having a cutting edge mounted on the frame adjacent the bedroll, the bedroll having an axially extending recess in the surface thereof and a rigid bearing surface within the recess, a resilient roll blade rigidly supported on the bearing surface and having an inclined outwardly extending free portion provided with a cutting edge, the bedroll being provided with a further recess adjacent the outwardly extending free blade portion for relieving said free blade portion for flexing, and a resilient compressible pad within said further recess adjacent the roll blade, the cutting edge of tHe anvil blade being positioned radially inwardly of the path of travel of the cutting edge of the roll blade to bring the edges of the blades into engagement during rotation of the bedroll whereby the roll blade is flexed and the pad is compressed.
 2. The apparatus of claim 1 in which the pad is substantially coextensive with the free blade portion of the roll blade.
 3. The apparatus of claim 1 in which the roll blade and the pad are of approximately the same thickness.
 4. The apparatus of claim 1 in which the depth of the further recess in a direction normal to the plane of the roll blade is slightly greater than the thickness of the pad.
 5. The apparatus of claim 4 in which the difference between the depth of the further recess and the thickness of the pad is about one-half of the distance through which the cutting edge of the roll blade is flexed into the further recess by the anvil blade.
 6. The apparatus of claim 1 in which the pad is compressed by about 10 percent to about 30 percent of its thickness by the flexing of the roll blade.
 7. The apparatus of claim 1 in which the said further recess has a depth normal to the plane of the roll blade of about 0.040 inch and the pad has a thickness of about 0.035 inch.
 8. The apparatus of claim 7 in which the cutting edge of the roll blade is flexed by the anvil blade a distance of about 0.010 inch from the plane of the roll blade.
 9. The apparatus of claim 1 in which the anvil blade extends at an angle of about 2.8* to the roll blade. 